Ore treatment process



Patented Mar. 25, 1947 I UNITED STATES- PATENT OFFICE,

2,418,073 ORE TREATMENT PROCESS Henry C. Kaweeki, Temple, Pa.

No Drawing. Application June 17, 1944,

Serial No. 540,896 r Claims. 1

This invention relates to ore treatment processes and more particularlyto a process for treating ores containing zirconium and titanium.

One of the objects of the present invention is to provide an improvedprocess for treating ores containing one of the metals zirconium andtitanium to recover the zirconium and titanium con- Still another objectis to provide an improved method of converting the oxide and silicatecompounds of zirconium and titanium into water soluble alkali metaldouble fluoride compounds.

A further object is to provide an economically practical method of"processing zirconium oxide and silicate ores to isolate therefom thezirconium content substantially free of associated metal impurities.

Other objects will be apparent as the invention is more fullyhereinafter disclosed;

In accordance with these objects I have discovered that the, highlyrefractory and chemically inert oxide and silicate compounds of themetals zirconium and titanium may be converted readily and easily intowater soluble alkali metal double fluoride compounds by sintering thesaid oxide or silicate compound with an alkali metal double fluoridecompound of a readily oxidized base metal such as, for example, analkali metal double fluoride compound of one of the metals Fe, Ni, Co,Cr and Zn.

I have discovered that when the refractory metal oxide, reduced to smallparticle size, is intimately admixed with the double fluoride compoundof the base metal, for example, with potassium ferric fluoride, and themixture is heated to elevated temperatures approximating 700 C. theoxide and double fluoride react to form an alkali metal zirconium doublefluoride and iron oxide. The reaction involved conforms essentially tothe following equations:

Titanium oxide and silicate react in a similar manner with the alkalimetal ferric fluoride to produce the double alkali metal titaniumfluoride. Any of the double fluoride compounds of the other metals,above identified, may be sub- (Cl. 23-18) v2 stituted for the irondouble fluoride without essential departure from the present invention.The alkali metal ferric fluoride, however, is the only such doublefluoride that is readily available 5 in sufilcient quantity and at aprice permitting use in the present invention at the present time.

The compound potassium. ferric fluoride (KaFeFe) m is old and well knownin the art and is best prepared by precipitation from aqueous solution.In this method, an aqueous solution of potassium fluoride, is acidifiedwith sulfuric acid to a pH of about 4 and an aqueous solution of ferricsulfate then is slowly added with constant agitation of the solutionuntil all of the fluoride present.

in the solution has been removed as alkali metal ferric fluorideprecipitate. An excess of 'theferric fluoride redissolves the doublefluoride and should be avoided. After settling, decanting, and

washing with clear water, the precipitated double fluoride may be airdried to tree the same of water.

The double (alkali metal-ferric) fluoride compound thus obtained is athermally stable compound. having a deflnite melting point approximating900 C. Nickel, cobalt, chromium,'zinc, and many other-base metals, formsimilar double fluoride compounds, as hereinbefore disclosed in GmelinHandbook, vol. 8 (1926) on pages 60 and 72.

The double fluoride compounds of zirconium and titanium have heretoforebeen recognized and prepared by methods generally involving the 5formation of an acid zirconium fluoride solution and precipitation ofthe double fluoride salt by the addition of an alkali metal fluoridethereto. Heretofore in the art it has also been recognized that the widedifference in the relative solubili- 40 ties of titanium and zirconiumdouble fluorides,

recognized that the double fluorides of zirconium and titanium may beformed in the manner herein disclosed and that by the practice of thisinvention the zirconium and titanium content of the oxide and silicateores or these metals may be selectively converted by a relatively simpleroasting operation into water soluble alkali metal double fluoridecompounds recoverable by a simple leaching operation from the oreresidues substantially free of any or the metals and silica usuallyassociated therewith in such ores.

present in the ore. a complicated series of chemical reaction stepsdesigned to efiectthe removal of the associated Asa specific embodimentof the practice of the present invention, but not as a limitation of thesame, the adaptation of the above disclosed invention to the recovery ofthe zirconium content of zirconium oxide and silicate ores will bedescribed. Each of the metals zirconium and titanium occurs widely innature and in many ores zirconium and titanium are present together insuch relative amounts as requires the practice of a complex chemicalprocess to obtain either element free of the other even after separatingthe two metals from other metals associated with them in the ores.

The major zirconium ores, however, are known in the art as zircon andbaddeleyite (or zirkite) which ordinarily contain a high percentage ofzirconium and only small percentages of titanium. Zircon is essentiallyzirconium silicate (arm-S102) of varying degrees of purity with thecommercial grades averaging about 65% Zr02 balance silica and varyingpercentages of the oxides of iron, aluminum, titanium, calcium, andother metals, which frequently include rare earths and thorium.Baddeleyite is essentially an oxide ore of varying degrees of puritywith the commercial grades averaging about 75% ZrOz; balance silica, andsubstantially the same associated metals above mentioned invaryingpercentages.-

Heretofore in the art, most ore treatment methods that have beenproposed for the recovery of zirconium from either the oxide or silicateore involve, first, an ore treatment step such as sintering, fusion, oracid treatment, which is designed to solubilize substantially all metalvalues This required the practice of solubilized impurities from thezirconium in solution to ultimatelyobtain some substantially purezirconium compound, such as the oxide, chloride or sulfate. By thepractice of the ore treatment step of the present invention thezirconium content of the zirconium ore only is solubilize'd and thepractice of any complicated series of purification steps subsequently toobtain the elimination of associated impurities thereby is eliminated.

. In accordance with the present invention, the

zirconium ore is mixed with an alkali metal double fluoride salt of abase metal such as iron, in an amount relative to the ZrOz content ofthe ore to obtain one of the two reactions indicated in Equations a andb above, and the mixture is heated to elevated temperatures within therange 600-800 C. effective to obtain the double decomposition reactionindicated. The sintered mixture then is cooled to atmospherictemperatures, reduced to small particle size, and is leached with water,preferably hot water, to extract the water soluble double fluoridecompounds of zirconium and titanium present therein, and the twocompounds in aqueous solution thereafter are separated, one from theother, by recrystallization from aqueous solution in accordance withknown practice based on the relative solubilities of the two compoundsin water at different temperatures. The chemically pure double fluoridesalts thus obtained thereafter may be converted into chemically pureoxide, chloride, sulfate and the like chemical compounds as may bedesired by methods also old and well known in the art.

In the practice of the present invention on zirconium ores, it isgenerally economically impractical to attempt to recover any of themetal conas an unavoidable by-product. With this in mind, I have devisedthe following process which is designed to effect, in the mosteconomically practical manner, the substantially complete recovery ofthe zirconium content of zirconium oxide and silicate ores with theminimum recovery of the titanium content of said ores. In thisadaptation of the present invention, the ore in its finely groundcondition is intimately admixed with potassium ferric fluoride in suchrelative proportions as is not over that empirically required inaccordance with Equations a and b to convert all of the zirconium todouble fluoride. This restriction limits the displacement reactioninvolved to the zirconium content of the ore.

The mixture is then compacted into suitable sized briquets or aggregatesand the briquets or aggregates are heated, in any convenient manner, toa temperature approximating 700 C. This temperature is maintained for anextended time interval, usually approximating one hour, to obtainsubstantially complete reaction between the ferric fluoride compound andzirconium oxide in the ore. The sintered material, after cooling andcrushin to small particle size, is then washed with hot water having atemperature approximating C. and a volume approximately sufllcient todissolveall of the zirconium double fluov ride present in the ore.

The potassium zirconium double fluoride has a solubility in pure Waterof about 1.4 grams per 100 grams H2O at 15 C. and 25 grams per 100 gramsH2O at 100 C. By limiting the volume of the leach water to thattheoretically required to obtain complete solution of the KzZlFe presentin the sinter with the formation of a substantially saturated solutionof the salt at the elevated temperature of the solution, I obtain acrystallizable solution of the double fluoride which, after filteringwhile hot, may be cooled naturally or artificially to 15 C. (or lower)to recover the zirconium salt present therein that is in excess of thesolubility limit at the lower temperature.

I have found that whereas the solubility of the corresponding potassiumtitanium fluoride in pure water approximates 1.28 grams per 100 gramsH2O at 20 C., the solubility of this salt in concentrated solutions ofthe potassium zirconium fluoride is much lower than this, and that bylimiting the amount of the ferric fluoride salt in the sinter mix to anamount less than that required to theoretically react with all of theZrOz content, the major portion of the titanium oxide present in the oreusually remainsunconverted to double fluoride even when present thereinin amounts as high as 3%. By subsequently leaching with a volume ofwater at 100 C/forming a concentrated solution of the double zirconiumfluoride the amount of the titanium double fluoride taken into solutionis still further reduced,

with the result that substantially pure zirconium doublefluoridecrystals are obtainable on the first crystallation from the leachsolution. One or more subsequent recrystallizations of the doublefluoride salt from pure water provides a double about 65% ZrO: is mixedwith about 3.8 parts (by weight) of the potassium ferric fluoride,formed into briquets and heated in a muflle furnace to 700 C. for onehour. About 97% of the ZrOa present in the ore may be recovered as watersoluble potassium zirconium double fluoride.

Considerable variation in the percent recovery of zirconium results fromvarying the manner of forming the mixture into briquets or aggregatesand in varying the relative particle sizes of the ore and ferric doublefluoride, as one skilled in the art will recognize. Best results appearto be obtained by the use of ore and ferric fluoride sized to pass about100 mesh screen which after mixing is moistened with water to form astiff mud having a consistency permitting the same to be molded intosmall sized bricks. ticular size of the bricks may be varied widelywithout departure from the present invention as may also the method andmode of heating the same to the desired temperature of about 700 C. Asthe apparatus required forms no part of the present invention and isotherwise old in the art it will not be described. On any large scaleproduction basis it is preferable to provide a continuous method ofsintering wherein the briquets are fed continuously into one end of anelongated furnace and-discharged from the other end. The time intervalwithin the furnace being regulated to obtain the particular reactiontime required with the size of brick employed.

I have found that I may lower the amount of the potassium ferricfluoride in the sinter mixture from the 3.8 parts, given above,'to aslow as 2.9

' parts without materially lowering the percent recovery of the ZrOzcontent of the ore and to obtain as added advantages a loweredconversion of the titanium to double fluoride and materially lower costsof operation. As an example, by using 2.9 parts per 1.9 parts of ore(65% ZrOz) the percent recovery of ZrOz as double fluoride saltapproximates 92%, while the amount of titanium double fluoride formed isstill further decreased, so that by using this ratio, substantiallyselective conversion of the Zr to double fluoride is obtained. Thislower ratio of ferric salt to Zl'Oz approximates a, one to one molecularweight ratio. The higher ratio approximates a 1 /3 to 1 ratio of salt tooxide as indicated in Equations a and b.

It is believed unnecessary to disclose the particular practice followingin leaching the ore and in crystallizing the leach solution as suchpractice is old and well known in the art and may be practiced in aplurality of different ways without essential departure from the presentinvention as one skilled in the art will readily perceive.

Economic factors, however, dictate the necessity of the repeated use ofthe first leach water to leach successive batches of sinter, thereby tomaintain the losses of the zirconium double fluoride (represented by theuncrystallized fraction therein) to a low constant. Thus by practicingthe sintering operation in such manner as to limit the amount oftitanium double fluoride formed to a low fraction percent, ashereinabove disclosed, a closed system of leaching may be evolvedproducing added economies of operation.

One of the major advantages of the present invention over processesheretofore proposed, lies in the feature of recovering the fluorinecontent of the double fluoride and in the leach waters,

in the form of an alkali metal ferric fluoride, for

return to the sintering step, thus forming a closed system affordingadded economies of. operation. In accordance with this feature of thepresent The par-- invention, the substantially pure zirconium doublefluoride crystals ultimately obtained are dis.

solved in pure water and the solution thus obtained is precipitated, inthe heretofore known manner, with potassium hydroxide. The zirconiumhydroxide thus obtained is washed free of potassium fluoride andconverted to oxide by ignition to elevated temperatures or,alternatively the hydroxide may be redissolved in a strong mineral acidsuch as HCl 01' H2804 to form the chloride or sulfate zirconium salt, ifdesired. The wash waters, containing potassium fluoride, are collected,and after acidification of the same to a pH of about 4 the fluorinecontent of thewash waters is precipitated as potassium ferric fluoridebythe addition thereto of ferric sulfate, as above described.

The first leach water after repeated re-use may be similarly treated forthe recovery of the fluoride content therein, as the concentration ofthe potassium fluoride and titanium double fluoride pounds watersoluble, which comprises finely di-- viding the said compounds, mixingthe same with therein becomes excessive for economic use. Alternatively,the zirconium content of the first leach water may, first, in major partbe recovered by reducing the volume of the solution by evaporation at C.until a concentrated potassium zirconium fluoride solution is obtained,which on cooling to 15 C. will crystallize out the double zirconiumfluoride present therein in excess of the solubility limit at this lowertemperature. In general, however, it will be found that the first leachwater accumulates considerable amounts of potassium fluoride as well asof titanium double fluoride, and that in the practice of the alternativeprocedure the double zirconium fluoride crystals obtained will becontaminated to a greater or lesser degree by one or both of theseimpurities, requiring the practice of at least one recrystallizationstepto remove the same therefrom. Various combinations of these twoprocedures may be employed whereby the bulk of the zirconium content ofthe primary leach water may be recovered and purified and the majorportion of the fluorine content converted to alkali metal ferricfluoride for return to the sintering step of the present invention.

The adaptation of the present invention to other zirconium ores and totitanium ores, for example, rutile or ilmenite, may be readily effectedas one skilled in the art may perceive from the above disclosure. Due tothe lower solubility of the titanium double fluoride considerably largerquantities of leach water must be employed than in the leaching ofzirconium ores. In general, in the practice of the present inventlon ontitanium ores containing low zirconium, all of the zirconium present inthe ore will be concentrated in the leach water to be recoveredtherefrom after the major portion of the titanium has been separatedtherefrom.

It is believed apparent from the above disclosure that the presentinvention may be widely adapted and widely modified without essentialdeparture therefrom and all such modifications and adaptations arecontemplated as may fall within the scope of the following claims.

What I claim is:

1. The method of treating the group of compounds consisting of the oxideand silicate compounds of zirconium and titanium to render the zirconiumand titanium content of said coman alkali metal double fluoride salt ofa metal selected from the group of metals consisting of Fe,

7 Ni, Co, Cr and Zn and heating the mixture to a temperature within therange 600800 C. for an extended time interval to convert the Zr and Tiinto water soluble fluozirconate and fluotitanate compounds.

2. The method of treating the oxideand silicate compounds of zirconiumand titanium to render the zirconium and titanium content of saidcompounds water soluble, which comprises finely dividing the saidcompounds, mixing the same with an alkali metal double fluoride salt ofa'metal selected from the group of metals consisting of Fe, Ni, Co, Crand Zn forming the mixture into agglomerates and heating theagglomerates to a temperature within the range 600- 800 C. for anextended time interval to convert 'the zirconium and titanium into watersoluble fluozirconate and fluotitanate compounds.

3. The method of treating the group of compounds consisting of the oxideand silicate cornpounds of zirconium to convert the zirconium content ofsaid compounds into water soluble alkali metal double fluoride compoundswhich comprises finely dividing said oxide and silicate compounds,mixing the said ,flnely divided compounds with an alkali metal ferricfluoride salt, and heating the mixture to a temperature within the rangeGOO-800 C. for an extended time interval.

4. The method of treating zirconium ores to recover the zirconiumcontent thereof as water soluble compounds which comprises finelydividing the ore, mixing the same with an alkali metal double fluoridesalt of a metal selected from the group of metals consisting of Fe, Ni,Co, Cr and Zn, heating the mixture to a temperature within the rangeGOO-800 C. for an extended time interval, leaching the sintered mixturewith water and recovering the zirconium from the leach water.

5. The method of solubilizing the zirconium content of ores containingthe oxide and silicate compounds of zirconium which comprises finelydividing the ore, mixing the ore with an alkali metal ferric'fluoridesalt in an amount providing from one to one and one-third molecularweights of salt for each molecular weightof zirconium present in theore, and heating the mixture to a temperature within the range GOO-800C. for an extended time interval approximating one hour.

6. The method of recovering the zirconium content of the oxide andsilicate compounds of zirconium which comprises finely dividing thecomfor each molecular weight of zirconium present therein, heating themixture to about 700 C. for

an extended time interval, leaching the sinter with hot water, andrecovering the zirconium from the said leach water.

7. The method of processing the group of ores consisting of the oxideand silicate ores of zirconium to obtain the zirconium content thereofsubstantially free from associated metal impurities, which comprisesmixing the ore inits finely divided state with potassium ferric fluoridein the proportions providing from one to one and one-third molecularweights of double fluoride for each molecular weight of ZrOz presenttherein, forming the mixture into aggregates, heating the aggreates toabout 700 C. for an extended time interval, cooling andlcrushing theheated aggregates, leaching the same with hot water, filtering the leachwater while hot, cooling the leach water to a lower temperature tocrystallize out the major portion of the potassium fluozirconatecompounds present therein, separating the fluozirconate crystals fromthe leach water, and recrystallizing the said fluozirconate at leastonce from pure water to purify the same. v

8. The method of claim 7, wherein the said leach water after separatingthe same from the fluozirconate crystals is reheated and re-used as aleach water on another batch of said heated aggregates.

9. The method of claim 'I, wherein the fluorine content of the leachwater and of all solutions used subsequently is conserved'and recoveredas potassium ferric fluoride for return to the sinter mixture.

10. The method of treating impure ZlOz to convert the same intosubstantially pure alkali metal fluozirconate compounds which comprisesmixing the oxide with an alkali metal double fluoride salt of a metalselected from the group'of metals con-- sisting of Fe, Ni, Co, Cr andZn, heating the mixing to 600-8 00 C. for an extended time interval,leaching the sintered mixture with hot water, filtering the leach waterwhile hot and cooling the same to a low temperature to precipitate HENRYC. KAWECKI.

